Similarity of Acid Proteinases Secreted by Candida albicans NIH A-207 and NIH B-792 Strains Cultured in BSA-Supplemented Medium

Abstract

Candidosis is an endogenous infectious disease occurring in a compromised host. Among the various Candida species, C. albicans is the most medically important. In 1961, Hasenclever and Mitchell 1,2) identified two serotypes in C. albicans species, A and B, demonstrating that the pathogenicity of both types was identical in mice when the inoculation of the cells was conducted via the intravenous route. The acid proteinase (AP) produced by the C. albicans species has attracted a great deal of attention as a virulence factor in the pathogenesis of human and animal infections, [3][4][5][6][7][8][9][10] though the existence of contradictory findings has been pointed out. 11,12) It has been shown that the recovery of the serotype A strains was more pronounced than that of serotype B in mice when both strains were orally inoculated with mixtures of the two strains.13) Borg and Rüchel 14) reported that different strains of serotype B, during infection into phagocytes, expressed an AP antigen only on blastoconidia, while filamentous cells of these strains appeared to be nonproteolytic, and that the serotype A strains expressed the antigen on the cells of both types.During the course of screening the proteinase-producing Candida strains, we found that the C. albicans NIH B-792 (serotype B) strain produced a large amount of AP in the culture broth compared to the C. albicans NIH A-207 (serotype A) strain when cultured in a yeast carbon-based medium supplemented with bovine serum albumin (BSA) as the sole nitrogen source. In this paper, we have compared the properties of the APs produced by the C. albicans NIH A-207 and NIH B-792 strains in order to determine the relevance of these enzymes in Candidosis. MATERIALS AND METHODS Organisms and Growth Conditions C. albicans NIH A-207 (serotype A) and C. albicans NIH B-792 (serotype B)strains, abbreviated A-207 and B-792, respectively, were kindly donated by Dr. T. Shinoda, Department of Microbiology, Meiji College of Pharmacy, Tokyo, Japan, and were maintained on Sabouraud agar. The organisms were routinely inoculated into 200 ml of 0.5% (w/v) of Sabouraud medium supplemented with yeast extract, and cultured in a rotary shaker (150 rpm) for 48 h at 27 ЊC. After cultivation, the organisms were collected by centrifugation, and washed three times with saline. The washed cells (5ϫ10 8 ) were then suspended in 1 ml of saline. To obtain the secretory AP, 1 ml of the washed cell suspension was cultured in 200 ml of growth medium containing 0.2% BSA and a 1.17% yeast carbon base in a 500 ml culture flask, and then further cultured for 2-3 d at 27 ЊC on a rotary shaker (150 rpm).Assay of AP Activity AP activity was determined as described by Kobayashi et al. 15) using bovine hemoglobin as the substrate. Briefly, a 0.4 ml portion of enzyme solution was added to 2 ml of substrate solution [6 g of bovine hemoglobin (Wako Pure Chemical Industries, Ltd., Osaka, Japan) in 1 l of 50 mM sodium citrate buffer (pH 3.6)] and the mixture was incubated at 37 ЊC for 60 min. The reaction was stoppe...

Comparison of Pathogenicity of Various Candida albicans and C. stellatoidea Strains

“…[21][22][23] However, no correlative variation in the pathogenicity and AP secretion was observed between the Candida strains as we already reported. 14,15) It has been reported that the efficacy of the acidic pH tolerance test for C. albicans has been confirmed only for isolates of the yeast species most commonly encountered in clinical specimens. 24) It is known that the Ca-A strain was able to clearely grow in acidic medium (pH 3-5), especially in pH 4.0, but was not observed at neutral media (pH 6, 7) by maintaining the pH of the media at fixed values throughout the cultivation.…”